As described in Patent Document 1 (Japanese Patent Application Publication No. H5-49090), one of factors for determining the frequency characteristic of a unidirectional dynamic microphone is an air chamber. In a handheld microphone, for example, for vocal use, the air chamber is usually provided in a grip housing formed in a cylindrical shape. One example of such a microphone is explained with reference to FIG. 5.
In a handheld unidirectional dynamic microphone, a grip housing 10 formed in a cylindrical shape by, for example, die casting is provided, and a microphone unit 20 is supported on one end side thereof. Although not shown, the microphone unit 20 incorporates a diaphragm fitted with a voice coil and a magnetism generating circuit having a magnetic gap, and the voice coil is arranged in the magnetic gap via the diaphragm so as to be capable of vibrating.
Because of being unidirectional, the microphone unit 20 is provided with a front audio terminal 20a and a rear audio terminal 20b. The microphone unit 20 is attached to one end side of the grip housing 10 via a connecting ring 11 in a state in which the rear end side thereof is airtightly inserted in the connecting ring 11. Between the connecting ring 11 and the grip housing 10, a shock mount member 12 exhibiting rubber elasticity is provided to reduce handling noise. Reference numeral 13 denotes a holding ring.
On the other end side of the grip housing 10 is integrally formed a connector storage portion 14, and an output connector 30 is mounted in the connector storage portion 14. The microphone unit 20 and the output connector 30 are connected to each other by a lead wire, not shown. The interior of the grip housing 10 is hollow, and functions as an air chamber 10a for the microphone unit 20.
In order to improve the tone quality in a low register, the volume of the air chamber 10a is preferably made large. Anyway, to obtain high directionality, it is necessary to prevent air from intruding into the air chamber 10a from the outside. For this purpose, in the conventional example, after the microphone unit 20 and the output connector 30 have been connected to each other by the lead wire, not shown, the output connector side is sealed by a sealing compound 15 such as silicon sealant applied into the grip housing 10.
However, the above-described conventional example has problems as described below. First, if an external force caused by tapping or rubbing is applied to the grip housing 10, the housing is displaced minutely, and accordingly the volume of the air chamber 10a in the grip housing 10 changes though minutely, which appears as handling noise.
Next, regarding the workability, the sealing compound is difficult to pour, and also waiting time is required before curing, so that the productivity is low. Also, when the output connector 30 is damaged and replaced, for example, by a drop shock and the like, the sealing compound 15 must be scraped off, which requires much time and labor.